Post on 06-Jan-2016
description
Ice- CreamFood Facts & Fallacies YSCN0006
I scream You scream We all scream for ice-cream
What is ice-cream? 1CoolSmoothYummy
What is ice-cream? 2WaterFatCarbohydrateProteinAir
What is ice-cream? 3Solid (at low temp)Liquid (at room temp)A colloidEmulsionFrozen foam
What is a Colloid ?Physical statesSolids, Liquids, Gases and.Stable mixtures of them are colloidsEmulsion, solid dispersed in a liquidFoam, gas dispersed in a liquid
Milk ~ Fat in water emulsion
Butter ~ Water in fat emulsion
Ice-cream
Sizesdissolved sugars, polysaccharides, proteinsfat globules 1 to 5 mice crystals 30 to 50 mair bubbles 50 to 100 m
Making ice creamIngredientsMixingFreezingHardening
IngredientsSucrose 15%Milk fat 15%(legal min. 10%)Non-fat milk solids 10%(lactose & casein)Corn syrup 5%(fructose & dextrins)Stabilisers 0.4%(polysaccharides)Emulsifier 0.2%(mono or di-glycerides)Water
Making ice-creamMixing of ingredients and homogenisation to give small fat globules.Pasteurisation to cook and sterilise the mixCooling, allows crystallisation of fat in globules
After homogenisationAddition of liquid flavoursColouringFruit puree
FreezingUses a scraped barrel freezerSimultaneous beating and freezingBeating to destabilize fat emulsionincorporate air
The Importance of Air- 40C- 5C
Not Enough Aira solid lump of ice?Too coldToo hardToo rich, percentage fat too high
Too Much AirDry textureMelts too quicklyCorrect quantity around 50% of volume= overrun of 100overrun is used to control the texture of ice-cream
After Freezingabout 50% water frozenSot texture =Soft serve ice-cream as used for conesParticulate addition, eg. nuts, biscuit crumbs, chocolate chipsPackaging
Freeze concentrationdissolved solutes depress the freezing point of a liquidthe higher the concentration the greater the depressionas the ice-cream water freezes the concentration of sugars increaseseven at very low temperatures there will be a small amount of unfrozen water present
HardeningContinuous blast freezer or batch freezer-40 Cremaining water frozenice-cream stable if kept below -25C
Ice crystals essential to stabilise air bubbles too big give a gritty texture small crystals formed by good nucleation rapid freezing ice crystals grow if temperature fluctuates
Emulsifiers & StabilisersEmulsifiershelp fat globule breakdownessential to stabilise air bubblesStabilisersreduce ice-crystal growth
Sugar crystalsformation of lactose crystals detectable as gritty sandiness in textureavoided by fast freezing and rapid formation of glass
Other IcesSorbet & water ices (no milk fat, high fruit)Sherbets (added citric acid)Frozen yoghourt (fermented milk solids)Ice-milk (3-5% milk fat)
Ice Bars & NoveltiesFormed by moulding or extrusionMoulding requires a stick!Centre filling possible with moulded barsAfter freezing products can be coated and enrobed
Dr Ramsdens special HKU chocolate ice -creamChocolate 60gMilk200mlCream400mlSugar150gVanilla10mlEgg yolk x 3
Preparation methodmelt chocolate & mix with milkmix egg yolks with sugaradd cream and vanilla to chocolate milk and bring to boilallow to cool & then add egg sugarmix at low heat for 15 min4C for 4 hoursfreeze for 30 minharden at 30C 12 h